材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
58 巻 , 8 号
選択された号の論文の12件中1~12を表示しています
特集 建設材料
総説
論文
  • 三田村 恒彦, 宮里 心一
    2009 年 58 巻 8 号 p. 666-671
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    In this study, the technique which estimated the change of corrosion rate of existing reinforced concrete under the temperature unsteadily changes was proposed. Therefore, in 2nd chapter, the change of corrosion rate was experimentally investigated using the mortar specimen exposed under the environment where the temperature changed. Next in 3rd chapter, the method for estimating internal temperature of mortar specimen and corrosion rate of the rebar from the temperature changes was constructed. Additionally in 4th chapter, the case which utilized this estimation method for corrosion survey of existing reinforced concrete was imagined. As a result, 1) the technique which estimated the corrosion rate under the temperature changes was able to be constructed. 2) By using this technique, it was clarified that quantity of rust in the any period could be estimated, if corrosion rate of existing reinforced concrete is investigated only at the once.
  • 三田 勝也, 辻 正哲
    2009 年 58 巻 8 号 p. 672-677
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    Crystallization pressure under dry condition after absorption of salts contained in seawater or rainwater causes surface deteriorations of concrete. This deterioration is emphasized under repetition of wetting and drying by propagation of micro cracks. However the deterioration has been hardly researched on concrete. On the other hand, initial curing condition must play an important role in the deterioration because the deterioration starts from surface and the curing has a major affect on the quality of surface concrete rather than inside concrete. In this study, the influence of initial curing condition, the kind of salt, type of cement and concrete mix proportion on the surface deterioration caused by salt crystallization pressure has been investigated. The salts investigated in wetting and drying test were Na2SO4, K2SO4, MgSO4, NaNO3, KNO3, Mg(NO3)2, NaCl, KCl and MgCl.
  • 三田 勝也, 辻 正哲
    2009 年 58 巻 8 号 p. 678-683
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    Inspection of reinforced concrete is important to ensure durability, and visual test is widely applied to the inspection. In this study, reliability on the result of the visual test for cold joint and sand streak was investigated, and it was clarified that error among the results of visual test comparing with photographs on questionnaires obtained by more than 100 students is fairly small. Then method to predict durability of reinforced concrete based on visual test results is proposed. The following (1), (2) and (3) are main conclusions.
    (1) The error in visual test by the proposed method among inspectors is significantly small enough to inspect cold joint and sand streak, even when the inspectors are students who have no experiences.
    (2) Relation between the visual test result for cold joint and the diffusion coefficient of chloride ion in hardened concrete is very close, so that the durability of reinforced concrete structure against chloride attack can be predicted based on visual test results. For a example, the method specified in Japan Society of Civil Engineers standard specification can be applied to the prediction.
    (3) Relation between the loss of mass under freezing and thawing test and the result of visual test for cold joint and sand streak is close, so that the visual test can be an effective method to predict durability against freezing and thawing and also to judge the requirement for repair.
  • 鎌田 敏郎, 内田 慎哉, 前 裕史, 山本 健太
    2009 年 58 巻 8 号 p. 684-690
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    Impact-echo method is a nondestructive testing method to estimate the thickness of concrete member. In this method, it is necessary to identify a single peak corresponding to resonance frequency of P-wave reflection between the surface and bottom of concrete plate. Thus, it is important to extract the targeted frequency component due to P-wave reflections. It is found that estimation of concrete thickness is not always easy because many peaks are often observed in the spectrum due to reflection at edge of concrete member. In this study, influence of shape and size of cross section on concrete thickness estimation by the impact-echo method was investigated. As a result, it was revealed that the problem of the generation of unrelated frequency peak for the estimation of concrete thickness could be solved by selecting impactor diameter to obtain 1.5∼3 times higher maximum useful frequency than the resonance frequency correspond to concrete thickness.
  • 渡辺 佳彦, 荒巻 智, 松田 好史, 山田 卓司, 宮川 豊章
    2009 年 58 巻 8 号 p. 691-696
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    Concrete surface coating method is one of the repair methods applied to deteriorated RC structures. By coating the concrete surface, coating materials protect the surface and prevent the harmful substances penetrating inside and deteriorated concrete debris dropping to third party. This method has been used with various techniques and materials. However its durability performance is not clear completely.
    The premature deterioration of San-yo Shinkansen RC Structures is mainly caused by carbonation, but this method applied to RC structures deteriorated by carbonation induced corrosion was few. Therefore, for upgrading the durability of this method when it is applied for the purpose of stopping further deterioration, on-site test and exposure specimen test have been continued since 2001 with 13 kinds of concrete surface coating materials. Various examinations (carbonation depth, bond strength, weathering resistance, and various kinds of permeability) have been carried out in 1, 3, and 5 years from the beginning. Test methods and their standards are also discussed.
  • 江良 和徳, 三原 孝文, 山本 貴士, 宮川 豊章
    2009 年 58 巻 8 号 p. 697-702
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    Recently, lithium ion pressurized injection method has been spotlighted as the repair method of concrete structure which deteriorated by ASR. In this study, the effect of lithium ion on ASR expansion was investigated. The elemental analysis of the ASR gel sample to which lithium ion had been supplied as also performed by using SEM, EPMA and TOF-SIMS. The change of the physical form of the ASR gel due to the supply of lithium ion was not found by SEM observation. However, the elemental analysis by TOF-SIMS enable to obtain the element mapping of the lithium ion in ASR gel. Furthermore, the elemental analysis by EPMA and TOF-SIMS demonstrated that lithium ion by the pressurized injection method has extended to the ASR gel. The compositional ratio of [Li] to [Na] in the ASR gel was able to be presumed.
論文
  • 津志田 雅之, 池田 良介, 北原 弘基, 安藤 新二
    2009 年 58 巻 8 号 p. 703-708
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    A fatigue testing machine for thin sheet specimens was developed to clarify the crystallographic orientation dependence on fatigue fracture behavior in magnesium single crystals. The size of the thin sheet specimen was 3mm in width and 0.3mm in thickness. One end of the thin sheet specimen was fixed at a voice coil of a loudspeaker and the other end was set free. A bending mode resonance occurs in the specimen due to forced vibration at the fixed end. To estimate stress amplitude, the displacement of the free end of the specimen was measured with a laser displacement meter. The stress amplitude was evaluated as the bending stress in the single cantilever. Fatigue tests were carried out with stress ratio R = –1 at room temperature in laboratory air and the frequency of the cyclic stress was 981Hz. In A-specimen whose surface plane and loading direction were (0001) and [1120], a fatigue crack propagated along [1100] at higher stress level while a crack propagated along [1210] at lower stress level. In B-specimen whose surface and loading direction were (1120) and [1100], a crack propagated partially along {1012} twin interface. As a result, fatigue life of the B-specimen was longer than that of the A-specimen. The fatigue limits of the A- and B-specimens were nearly the same, and it was estimated as 45MPa at 106∼108 cycles. The fatigue testing machine developed in this study showed the crystallographic orientation dependence on fatigue fracture behavior in magnesium single crystals.
  • 加藤 孝憲, 菅田 淳, 中山 英介
    2009 年 58 巻 8 号 p. 709-714
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    Spalling is one of the typical failures of railway wheels. Spalling is rolling contact fatigue (RCF) damages, as the result of unexpected wheel slides on the rail. One of the major characteristics of spalling is that a part of the wheel surface transforms to white layers by a frictional heat of the slides. In this study, in order to evaluate the influence of white layer geometries and material strengths on the spalling properties of the wheel steels, RCF tests and elastic-plastic FEM analyses were carried out. Moreover, the Dang Van model, which is one of the multiaxial fatigue strength evaluation methods, was applied to predict the white layer's fatigue strength in RCF tests. There are three main results from this study. Firstly, RCF tests yielded that the crack initiations were less in the smaller white layers than in the larger ones. In addition, the crack initiations from the white layers were less in the higher strength of the matrix than in the lower strength of it. Secondly, FEM analysis results showed that the maximum stresses were lower in the smaller white layers than in the larger ones. The maximum stresses of the white layers also were lower in the higher strength of the matrix than in the lower strength of it. These results corresponded to the crack initiation behaviors of RCF tests. Finally, the fatigue strength prediction results by the Dang Van model were reasonably equivalent to the spalling properties obtained by RCF tests. Therefore it was concluded that the white layer geometries and the strength of the matrix much influenced the spalling properties, and these results were predicted by the fatigue strength evaluation method that we proposed.
  • 斎藤 豪, 内田 雄久, 李 允燮, 大即 信明
    2009 年 58 巻 8 号 p. 715-720
    発行日: 2009/08/15
    公開日: 2009/08/15
    ジャーナル フリー
    This research focuses on (1) the relationship between the development of compressive strength of blast furnace cement and hydrated products, hydration behavior and porosity in early stage at 5°C, 20°C and 40°C. Also, the purpose of this research is (2) to investigate the hydration behavior, compared with 20°C. As a result, in early age at 5°C, only ettringite and C4AH13 are generated without generation of monosulfate, and development of compressive strength of blast furnace cement is different from those at 20°C and 40°C. It is concluded that (1) the reaction ratio of BFS at 5°C is lower, then (2) hydration behavior and hydration products at 5°C are different from those at 20°C and 40°C, finally, (3) pore in the hardened body at 5°C cannot be filled adequately.
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